1. Field of the Invention
The invention relates to a robotic device. More particularly, the invention relates to a robotic device having an arm and a hand.
2. Description of the Related Art
A robotic device having an arm and a hand has been proposed, the practical use of which is anticipated in not only industrial fields, but a variety of fields such as healthcare, agriculture, and safety systems. In particular, in the field of healthcare, the working population is expected to decrease and the number of those requiring nursing care is expected to increase with the declining birthrate and the aging population, so expectations are high for robotic devices that coexist with people and assist with actual work in the same environment as people.
For example, in nonpatent reference 1 (Sasaki, Daisuke; Noritsugu, Toshiro; and Takaiwa, Masahiro. Development of Pressure Measurement Type Tactile Soft Sensor for Live Assist Robot. Japan Society of Mechanical Engineers, Transactions of the Japan Society of Mechanical Engineers, C 70 (689) pp. 77-82, January 2004), a robotic device is proposed in which a pressure sensor is arranged on the end of a finger of a multi-fingered hand which is attached to the end of a robot arm. The robot device proposed in nonpatent reference 1 wipes the forearm of a person by moving the arm along the forearm of the person while simultaneously controlling the finger joints of the fingers on the hand so that the pressing force detected by pressure sensors in the fingertips matches a target value while the fingertips are touching the forearm of the person.
However, with the robotic device according to the technology described above, only the fingertips contact the object, e.g., the forearm, of the person so the contact area is small which translates into poor work efficiency. That is, in the technology described above, the whole surface of the base (i.e., the palm) of the hand does not track (i.e., conform to) the surface of the object. However, when the entire surface of the hand does contact the object, the dynamic model with multipoint contact becomes complex. While the pressing force of the palm can be adjusted by force control of the arm, the force generated by the hand and the force generated by the arm affect one another so the relationship between the pressing force generated by force control of the arm and the pressing force that is actually generated over the entire area of the hand is not fixed. Therefore, it is necessary to have force control that coordinates the arm and the hand. However, it is difficult to perform force control for tracking the surface of the object with the whole surface of the hand in which the arm is coordinated with the hand, based on an analysis of the complex dynamic model of multipoint contact.